U.S. patent number 6,885,270 [Application Number 10/470,004] was granted by the patent office on 2005-04-26 for wire core inductive devices having a biassing magnet and methods of making the same.
Invention is credited to Harrie R. Buswell.
United States Patent |
6,885,270 |
Buswell |
April 26, 2005 |
Wire core inductive devices having a biassing magnet and methods of
making the same
Abstract
An inductive device comprises a magnetic core including a
portion of a plurality of wires, at least one electric winding
extending around the magnetic core, each of the plurality of wires
substantially encircling the at least one electric winding, and at
least one biassing magnet disposed adjacent the plurality of wires
to provide a bias magnet flux for offsetting a flux generated by a
direct current component flowing in the winding.
Inventors: |
Buswell; Harrie R. (Berea,
KY) |
Family
ID: |
23002608 |
Appl.
No.: |
10/470,004 |
Filed: |
July 23, 2003 |
PCT
Filed: |
January 23, 2002 |
PCT No.: |
PCT/US02/01664 |
371(c)(1),(2),(4) Date: |
July 23, 2003 |
PCT
Pub. No.: |
WO02/05991 |
PCT
Pub. Date: |
August 01, 2002 |
Current U.S.
Class: |
336/83; 29/602.1;
336/233 |
Current CPC
Class: |
H01F
3/06 (20130101); H01F 30/16 (20130101); H01F
41/02 (20130101); H01F 27/36 (20130101); H01F
27/34 (20130101); H01F 2003/103 (20130101); H01F
17/06 (20130101); Y10T 29/4902 (20150115) |
Current International
Class: |
H01F
3/00 (20060101); H01F 41/02 (20060101); H01F
3/06 (20060101); H01F 27/36 (20060101); H01F
17/06 (20060101); H01F 27/34 (20060101); H01F
027/02 () |
Field of
Search: |
;336/83,233,60,234,229
;29/602.1,606 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mai; Anh
Attorney, Agent or Firm: Miles & Stockbridge P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of provisional Application No.
60/263,637, filed on Jan. 23, 2001, which is incorporated herein by
reference.
Claims
What is claimed is:
1. An inductive device comprising: a magnetic core including a
portion of a plurality of wires; at least one electric winding
extending around said magnetic core, each of said plurality of
wires at least partially encircling said at least one electric
winding and completing a magnetic circuit; and at least one
biassing magnet disposed adjacent said plurality of wires and
applying a magnetic bias to said magnetic circuit.
2. An inductive device as recited in claim 1, wherein said biasing
is a permanent magnet.
3. An inductive device as recited in claim 1, wherein at least one
of said plurality of wires substantially encircles said biassing
magnet.
4. An inductive device as recited in claim 1, wherein said biassing
magnet is disposed at an end of the inductive device.
5. An inductive device as recited in claim 1, wherein said biasing
magnet is disposed at an end of said magnetic core.
6. An inductive device as recited in claim 5, wherein at least one
of said plurality of wires substantially encircles said biassing
magnet.
7. An inductive device as recited in claim 1, further comprising a
second biassing magnet, wherein said one biassing magnet and said
second biassing magnet are disposed at opposite ends of said
magnetic core.
8. An inductive device as recited in claim 7, wherein at least one
of said plurality of wires substantially encircles said biassing
magnet and said second biassing magnet.
9. An inductive device as recited in claim 1, wherein said biassing
magnet is a hollow cylinder substantially encircling said plurality
of wires.
10. An inductive device as recited in claim 1, wherein said
biassing magnet is disposed adjacent said magnetic core.
11. An inductive device as recited in claim 1, wherein said
biassing magnet is a hollow cylinder substantially encircling a
portion of said magnetic core.
12. An inductive device as recited in claim 1, wherein said
biassing magnet is a hollow cylinder substantially encircling said
magnetic core.
13. An inductive device as recited in claim 1, wherein said
biassing magnet is disposed among said portion of said plurality of
wires of said magnetic core.
14. An inductive device as recited in claim 10, wherein said
biassing magnet is a cylindrical.
15. An inductive device as recited in claim 1, wherein said
plurality of wires include wires of different cross-sections
arranged to increase the density of said magnetic core.
16. An inductive device as recited in claim 1, wherein said
plurality of wires substantially envelop said at least one electric
winding to provide shielding from electromagnetic fields.
17. An inductive device as recited in claim 1, wherein each of said
plurality of wires includes a first end and a second end that
substantially abut one another.
18. An inductive device as recited in claim 17, wherein said first
and second ends of each wire meet.
19. An inductive device as recited in claim 17, wherein said first
and second ends of each wire are secured in place.
20. An inductive device as recited in claim 19, wherein said first
and second ends of said plurality of wires are secured by a
band.
21. An inductive device as recited in claim 1, wherein each of said
plurality of wires includes a first end and a second end that
oppose one another across a gap, and said biassing magnet is
disposed adjacent said gap.
22. An inductive device as recited in claim 21, wherein said
biassing magnet is received in said gap.
23. An inductive device as recited in claim 1, further comprising a
mounting post disposed among said plurality of wires and extending
from said plurality of wires.
24. An inductive device as recited in claim 23, wherein the
mounting post extends from said plurality of wires only at one end
of the inductive device.
25. An inductive device as recited in claim 1, further comprising a
second electric winding extending around said magnetic core.
26. An inductive device as recited in claim 25, wherein said second
electric winding is axially displaced from said at least one
electric winding.
27. An inductive device as recited in claim 25, wherein said second
electric winding is arranged concentrically with said at least one
electric winding.
28. An inductive device as recited in claim 1, wherein said at
least one electric winding is in direct contact with said magnetic
core.
29. An inductive device as recited in claim 1, wherein said
plurality of wires are electrically insulated from one another.
30. A method for making an inductive device, comprising: providing
a magnetic core including a portion of a plurality of wires,
arranging at least one electric winding around the magnetic core;
configuring each of the plurality of wires so as to at least
partially encircle the at least one electric winding and complete a
magnetic circuit; and providing at least one biassing magnet
adjacent the plurality of wires to apply a magnetic bias to said
magnetic circuit.
31. A method as recited in claim 30, wherein at least one of said
plurality of wires substantially encircles said biassing
magnet.
32. A method as recited in claim 31, wherein said biassing magnet
is disposed at an end of said magnetic core.
33. A method as recited in claim 30, wherein said biassing magnet
is disposed at an end of said inductive device.
34. A method as recited in claim 30, further comprising providing a
second biassing magnet, wherein said biassing magnet and said
second biassing magnet are disposed at opposite ends of said
magnetic core.
35. A method as recited in claim 34, wherein at least one of said
plurality of wires substantially encircles said one biassing magnet
and said second biassing magnet.
36. A method as recited in claim 30, wherein the plurality of wires
include wires of different cross-sections arranged to increase the
density of the magnetic core.
37. A method as recited in claim 30, wherein said configuring
includes substantially abutting first and second ends of each of
the plurality of wires.
38. A method as recited in claim 30, wherein said configuring
includes securing first and second ends of each of the plurality of
wires in place.
39. A method as recited in claim 38, wherein said securing includes
wrapping a band around the plurality of wires.
40. A method as recited in claim 38, wherein said biassing magnet
is a permanent magnet.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of inductive devices,
and more particularly to wire core inductive devices such as
transformers, chokes, coils, ballasts, and the like.
2. Description of Related Art
It is common for low frequency application transformers and other
inductive devices to be made up of a magnetic core comprising a
plurality of sheets of steel, the sheets being die cut and stacked
to create a desired thickness of the core. For many years, the
thickness (thus number of necessary pieces) of the stampings has
been determined by a strict set of constraints, e.g. magnitude of
eddy currents versus number of necessary pieces. The individual
sheets of selected thickness are oxide-coated, varnished or
otherwise electrically insulated from one another in order to
reduce/minimize eddy currents in the magnetic core.
The present inventor has developed wire core inductive devices such
as transformers, chokes, coils, ballasts, and the like having a
magnetic core including a portion of a plurality of wires rather
than the conventional sheets of steel. The ends of the plurality of
wires extend around the electrical windings and are arranged to
substantially complete a magnetic circuit or flux path. These
devices and related methods of manufacturing these devices are set
forth in detail in U.S. Pat. Nos. 6,239,681 and 6,268,786, which
are incorporated herein by reference. One important aspect of these
devices is the provision of an increased operating frequency span
enabling higher operating frequencies over conventional E/I type
units. These increased operating frequencies approach those
previously only efficiently and effectively reached by switch-mode
power supplies, inverters, and converters which contained molded
core type transformers.
A magnetic core of an inductive device will reach a magnetic
saturation point when a sufficient magnetic force is applied to the
core by current flowing through windings extending around the core.
Saturation of the core is often a non-desirable condition because
the inductance provided by the device drops drastically. In
applications where a direct current component is present in a
current flowing in a winding of an inductive device, the core will
reach saturation more rapidly because the direct current component
provides a magnetic bias.
SUMMARY OF THE INVENTION
This invention provides a wire core inductive device that includes
a biassing magnet to provide a bias magnetic flux. The bias
magnetic flux offsets a flux component generated by a direct
current component of a current flowing in one or more windings
around the core. The biassing magnet thereby allows saturation of
the magnetic core to occur at a higher current level. Accordingly,
the useful range of the wire core inductive device is improved over
a similar inductive device without the biassing magnet. In a
preferred embodiment, the biassing magnet is a permanent magnet,
which is also highly electrically resistive (to reduce eddy
currents).
Thus, awarding to one of its principal aspects, the present
invention provides an inductive device having a magnetic core
including a portion of a plurality of wires, at least one electric
winding extending around the magnetic core with each of the
plurality of wires substantially encircling the at least one
electric winding and completing a magnetic circuit, and at least
one biassing magnet disposed adjacent to the plurality of wires and
applying a magnetic bias to the magnetic circuit.
According to another of its principal aspects, the present
invention provides a method for making an inductive device,
comprising the steps of providing a magnetic core including a
portion of a plurality of wires, winding at least one electric
winding around the magnetic core, configuring each of the plurality
of wires so as to substantially encircle the at least one electric
winding and complete a magnetic circuit, and providing at least one
biassing magnet adjacent to the plurality of wires to apply a
magnetic bias to the magnetic circuit.
In preferred embodiments, the electric windings are either wound
directly onto the magnetic core or are wound separately and slipped
over an end of the core, and the inductive device includes a
biassing magnet, which is slipped over the end of the magnetic
core. The ends of the wires forming the magnetic core are spread
and configured to substantially encircle the electric windings and
the biassing magnet, forming a complete magnetic circuit. A band or
other connector means holds the ends of the wires together.
Advantageously, the wires configured in this manner envelop the
electric windings and the biassing magnet to provide a shield
substantially containing the electromagnetic fields emanating from
the device and reducing the intrusion of electromagnetic fields
from external sources. The shielded inductive device may include at
least one additional magnet positioned adjacent the plurality of
wires to further enhance the offsetting bias of the biassing
magnet.
A preferred embodiment of a method of making an inductive device
according to this invention, includes providing a magnetic core
formed from a plurality of wires, placing at least one electric
winding along the length of the core, providing at least one
permanent magnet adjacent to the core, and configuring the
plurality of wires to substantially envelop the at least one
electric winding and biassing magnet and form a complete a magnetic
circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other aspects, features and advantages of this
invention will be more appreciated from the following detailed
description of the preferred embodiments with reference to the
accompanying drawings, wherein:
FIG. 1 is a perspective view of an inductive device according to a
preferred embodiment of the invention;
FIG. 2 is a cross-sectional view of the inductive device taken
along line II--II in FIG. 1;
FIG. 3 is a cross-sectional view similar to FIG. 2 but showing an
inductive device according to an alternative embodiment of the
invention, wherein electric windings are axially displaced from
each other on the magnetic core and two permanent magnetic rings
are disposed at opposite ends of the magnetic core;
FIGS. 4-9 are cross-sectional views showing, in more diagrammatic
form, alternative embodiments of inductive devices according to the
present invention;
FIG. 10 is a cross-sectional view taken along line X--X of FIG.
9;
FIGS. 11-13 are similar to the cross-sectional view of FIG. 10, but
show alternative cross-sectional shapes for a permanent magnet
disposed among wires of a magnetic core;
FIG. 14 is a cross-sectional view showing, in more diagrammatic
form, yet another embodiment of an inductive device according to
the present invention;
FIG. 15 is a cross-sectional view taken along line XV--XV of FIG.
14;
FIG. 16 is a cross-sectional view showing, in more diagrammatic
form, another embodiment of an inductive device according to the
present invention;
FIG. 17 is an illustration for explaining a method according to a
preferred embodiment of the invention including forming a magnetic
core by gathering a plurality of wires pulled from a creel to form
a bundle, securing the wires with bands, and severing the bundled
wires;
FIG. 18 is an illustration showing an electric winding formed
directly on the magnetic core according to a preferred embodiment
of the invention;
FIGS. 19 and 20 are illustrations for explaining an alternative
embodiment of a method for forming a magnetic core by winding one
or a plurality of wires on a spindle, and severing the wound wires
to form the core; and
FIG. 21 is an illustration for explaining a method including
extending the plurality of wires over the electric windings to
envelop the windings in accordance with a preferred embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows an inductive device 10 according to a preferred
embodiment of the invention. In this embodiment, the inductive
device 10 is a transformer. However, it should be appreciated that
the principles of this invention are applicable to a variety of
inductive devices, such as, but not limited to: transformers and
coils (chokes, reactors, etc.) both of types that utilize core
saturation (saturable transformers, magnetic amplifiers, saturable
reactors, swinging chokes, etc.) and those that do not, as well as
AC applications of solenoids, relays, contactors, and linear and
rotary inductive devices.
The inductive device 10 includes leads 12 for connecting a power
source (not shown) to a primary winding of the inductive device 10.
The inductive device 10 also includes leads 14 for connecting a
secondary winding to a load (not shown). Those skilled in the art
will realize that the designation of the primary and secondary
windings is somewhat arbitrary, and that one may use the leads 14
for connection to the primary winding, and the leads 12 for
connection to the secondary winding. The designations of "primary"
and "secondary" are therefore used herein as a convenience, and it
should be understood that the windings are reversible.
FIG. 2 is a cross-sectional view of the inductive device 10 taken
along the line II--II in FIG. 1. The inductive device 10 includes a
magnetic core 16 formed of a plurality of wires 18. The electric
windings 20 and 22 extend around the magnetic core 16. In this
exemplary embodiment, the electric winding 22 also extends around
the electric winding 20.
A biassing magnet 24 is slipped over the end of the magnetic core
16. In this embodiment, the biassing magnet 24 is a permanent
magnet. Further, the biassing magnet 24 is ring shaped. It should
be appreciated that in other embodiments, the biassing magnet may
be an electromagnet or a combination of a permanent magnet and an
electromagnet.
The plurality of wires 18 utilized to form the magnetic core 16
extend outwardly therefrom and are further formed to encircle
electric windings 20 and 22 and the biassing magnet 24 so as to
complete a magnetic circuit The ends of the plurality of wires 18
meet, and are held together by a band 28 or the like. The leads 12
and 14 pass between the plurality of wires 18 to connect to the
electric windings 20 and 22, respectively. Alternatively, the ends
of the plurality of wires 18 may be joined above or below the
magnetic core 16 or additional wires (not shown) may be used to
join the end of the plurality of wires 18.
The wires 18 form a shield that substantially contains
electromagnetic fields emanating from the inductive device 10 and
that also reduces the intrusion of electromagnetic fields including
electromagnetic interference and/or magnetic flux from external
sources.
The biassing magnet 24 is arranged on the core, so that it provides
a magnetic bias to the magnetic circuit (indicated by arrows A) to
offset a magnetic bias generated by a direct current component
flowing through either or both of the windings 20 and 22 (indicated
by arrows B). It will be appreciated that reversing the polarity of
the biassing magnet 24 can reverse the offsetting magnetic
bias.
The inductive device 10 also includes a mounting post 26 and a band
28 as shown and described in the aforementioned U.S. Pat. Nos.
6,239,681 and 6,268,780.
FIG. 3 is a cross-sectional view similar to FIG. 2, but shows an
inductive device 30 according to an alternative embodiment of this
invention. The inductive device 30 is similar to the inductive
device 10, in that it includes a magnetic core 32 formed of a
portion of a plurality of wires 34 and electrical windings 36 and
38, which extend around the magnetic core 32. The plurality of
wires encircle the windings 36 and 38, completing a magnetic
circuit. Leads 40 and 42 connect to windings 36 and 38,
respectively. Similar to the inductive device 10, a biassing magnet
44 is disposed adjacent to the plurality of wires 34. The biassing
magnet 44 is a permanent magnet.
The electrical windings 36 and 38 are positioned axially beside one
another on magnetic core 32, rather than concentrically as in the
inductive device 10 of FIG. 2. In addition, a second biassing
magnet 46 is provided. The second biassing magnet 46 is also a
permanent magnet.
The biassing magnet 44 and the second biassing magnet 46, both of
which are ring shaped, are slipped over opposite ends of the
magnetic core 32. The plurality of wires 34 substantially encircle
the windings 36 and 38 as well as the biassing magnets 44 and 46.
The biassing magnets 44 and 46 provide a combined offsetting
magnetic bias (indicated by arrows C) to counteract a bias produced
by a direct current (indicated by arrows D).
The inductive device includes a mounting post 48 that extends
axially from the magnetic core 32 at one end.
FIG. 4 is a cross-sectional view of an inductive device 50
according to an alternative embodiment of the present invention.
The inductive device 50 includes a magnetic core 52 that is formed
of a portion of a plurality of wires 54. A primary winding 56 and a
secondary winding 58 are wrapped around the magnetic core 52. As in
the above embodiments, the plurality of wires 54 encircle the
windings 56 and 58 so as to form a complete magnetic circuit and
provide an electromagnetic shield 60.
In the present embodiment, a biassing magnet 62 is disposed at one
end of the inductive device 50. The biassing magnet 62 is a
permanent magnet that is substantially non-electrically conductive
(to reduce eddy currents). It should be appreciated that in other
embodiments, the biassing magnet 62 may be an electromagnet or a
combination of a permanent magnet and an electromagnet. The
biassing magnet 62 is disposed on an outer surface of the plurality
of wires 54. The biassing magnet 62 substantially covers an end of
the inductive device 50. However, it should be appreciated that the
biassing magnet 62 may cover only a portion of the end depending
upon the requirements of the particular application. The biassing
magnet 62 is arranged on the device 50 so that it provides a
magnetic bias, (indicated by arrows E) to offset a magnetic bias
that is introduced when a direct current component flows through
any of the windings 56 and 58 (indicated by arrows F).
The biassing magnet 62 is disc shaped in this embodiment. However,
it should be appreciated that the biassing magnet 62 may be other
shapes such as, but not limited to, ring, cylindrical or
rectangular. It should further be appreciated that in other
embodiments, the biassing magnet 62 may include or be replaced by a
plurality of biassing magnets.
FIG. 5 is a cross-sectional view of an inductive device 70
according to another embodiment of this invention. The inductive
device 70 includes the magnetic core 72 that includes a portion of
a plurality of wires 74. The device 70 also includes a primary
winding 76 and secondary winding 78 wrapped around the magnetic
core 72. The plurality of wires 74 substantially encircle the
windings 76 and 78 so as to complete a magnetic circuit and provide
an electromagnetic shield 80. Inductive device 70 also includes a
first biassing magnet 82 and a second biassing magnet 84 disposed
at opposite ends of the inductive device 70. The biassing magnets
82 and 84 are disposed on an outer surface of the plurality of
wires 74. The biassing magnets 82 and 84 are disc shaped and in
this embodiment, they are permanent magnets. However, it should be
appreciated that the biassing magnets 82 and 84 may be other shapes
such as, but not limited to, ring, cylindrical, or rectangular. It
should further be appreciated that in other embodiments, either or
both biassing magnets 82 and 84 may be replaced with plurality of
biassing magnets. The biassing magnets 82 and 84 provide a combined
offsetting magnetic bias (indicated by arrows G) to counteract a
bias produced by a direct current (indicated by arrows H) flowing
in one of the windings.
FIG. 6 is a cross-sectional view of an inductive device 90
according to another alternative embodiment of the present
invention. The inductive device 90 is similar to the inductive
device 60 in that it includes a magnetic core 92 formed of a
portion of a plurality of wires 94. The inductive device 90 also
includes a primary winding 96 and a secondary winding 98 disposed
around the core 92. The plurality of wires 74 substantially
encircle the windings 96 and 98 so as to complete a magnetic
circuit and provide an electromagnetic shield 100. The inductive
device further includes a biassing magnet 102. The biassing magnet
102 is disposed adjacent to the shield 100. In this embodiment, the
biassing magnet 102 is a permanent magnet and is disposed
substantially parallel to the magnetic core 92. The biassing magnet
102 extends partially around the shield 100, but may extend
substantially around the shield 100. The biassing magnet 102 is
preferably shaped to conform to the contour of the shield. However,
this is not strictly necessary. It should further be appreciated
that in other embodiments, the magnetic element 102 may include or
be replaced by a plurality of magnetic elements.
The biassing magnet 102 is arranged on the device 90, so that it
provides a magnetic bias (indicated by arrows I) to offset a
magnetic bias that is introduced when a direct current component
flows through either of the windings 96 and 98 (indicated by arrows
J). It will be appreciated that reversing the polarity of the
biassing magnet 102 can reverse the offsetting magnetic bias.
FIG. 7 is a cross-sectional view of an inductive device 110
accordingly to another alternative embodiment of the present
invention. The inductive device 110 is similar to the previous
embodiments of inductive devices in that it includes a magnetic
core 112 formed of a portion of a plurality wires 114. The
plurality of wires 114 encircle a primary winding 116 and a
secondary winding 118 disposed around the magnetic core 112. The
plurality wires 114 form a magnetic circuit and an electromagnetic
shield 120. The inductive device 110 further includes a biassing
magnet 122, which is a permanent magnet in this embodiment. The
biassing magnet 122 is a hollow cylinder having an interior space
124. The magnetic core 112, the primary winding 116, the secondary
winding 118, and the shield 120 are substantially disposed within
the interior space 124. The biassing magnet 122 is arranged so that
it provides a magnetic bias (indicated by arrows K) to offset a
magnetic bias that is introduced when a direct current component
flows through either of the windings 116 and 118 (indicated by
arrows L). It will be appreciated that reversing the polarity of
the biassing magnet 122 can reverse the offsetting magnetic
bias.
FIG. 8 is a cross-sectional view of an inductive device 130 of an
alternative embodiment of the present invention. The inductive
device 130 is similar to the previous inductive devices as
referenced above in that it includes a magnetic core 132 formed of
a portion of a plurality of wires 134, a primary winding 136, a
secondary winding 138, a shield 140, and a biassing magnet 142. The
plurality of wires 134 at least partially encircle the windings 136
and 138 and the biassing magnet 142, to complete a magnetic circuit
and to form the shield 140. The biassing magnet 142 is a permanent
magnet.
The biassing magnet 142 in this embodiment is a hollow cylinder
having an interior space 144. The magnetic core 132 extends through
the interior space 144. The electric windings 136 and 138 are
disposed around the biassing magnet 142. The biassing magnet 142 is
arranged adjacent the plurality of wires 134 so that it provides a
magnetic bias (indicated by arrows M) to offset a magnetic bias
that is introduced when a direct current component flows through
either of the windings 136 and 138 (indicated by arrows N). It will
be appreciated that reversing the polarity of the biassing magnet
142 can reverse the offsetting magnetic bias.
FIG. 9 is a cross-sectional view of an inductive device 150 of
another alternative embodiment of the present invention. The
inductive device 150 is similar to the above reference inductive
devices in that it includes a magnetic core 152 formed of a portion
of a plurality of wires 154, a primary winding 156, a secondary
winding 158, an electromagnetic shield 160 and a biassing magnet
162, with the plurality of wires 154 at least partially encircling
the windings 156 and 158 so as to complete a magnetic circuit and
form the shield 160.
The biassing magnet 162 in this embodiment is a permanent magnet in
the form of a bar. The biassing magnet 162 is disposed among the
wires of the magnetic core 152. In this exemplary embodiment, the
portions of the plurality of wires that make up the magnetic core
152 are disposed along outer surface of the biassing magnet 162, as
shown in FIG. 10, which is a cross-sectional view taken along line
X--X in FIG. 9. The biassing magnet 162 is a cylinder in this
embodiment.
The biassing magnet 162 is arranged adjacent the plurality of wires
154, so that it provides a magnetic bias (indicated by arrows O) to
offset a magnetic bias that is introduced when a direct current
component flows through either or both of the windings 156 and 158
(indicated by arrows P). It will be appreciated that reversing the
polarity of the biassing magnet 162 can reverse the offsetting
magnetic bias.
FIGS. 11 through 13 show other cross-sectional shapes of magnetic
elements that may be utilized in the inductive device 150 in place
of magnetic element 162. FIG. 11 shows a biassing magnet 164 having
a cross shape. FIG. 12 shows a biassing magnet 166 having a
semi-circular shape, and FIG. 13 displays a biassing magnet 168
having a U-shape. It should be appreciated that the biassing magnet
of the inductive device 150 may be any one of a variety of
different shapes in other embodiments.
FIG. 14 is cross-sectional view of an inductive device 170
according to another embodiment of the present invention. The
inductive device 170 is similar to the inductive devices referenced
above, in that it includes a magnetic core 172 formed of a portion
of a plurality of wires 174, a primary winding 176, a secondary
winding 178, an electromagnetic shield 180 and a biassing magnet
182, which is a permanent magnet. The plurality of wires 174 at
least partially encircle the windings 176 and 178 so as to complete
a magnetic circuit and form the shield 180.
The biassing magnet 182 is a hollow cylinder having an interior
space 184. The biassing magnet 182 is disposed along the portion of
the plurality of wires that make up the magnetic core 172, and at
least part of the magnetic core extends through the interior space
184 with the other wires of the core being disposed along the outer
surface of the biassing magnet 182. The hollow-cylindrical shape of
the biassing magnet 182 is illustrated in FIG. 15, which is a
cross-sectional view taken along line XV--XV in FIG. 14.
The biassing magnet 182 is arranged adjacent the plurality of wires
174, so that it provides a magnetic bias (indicated by arrows Q) to
offset a magnetic bias that is introduced when a direct current
component flows through either or both of the windings 176 and 178
(indicated by arrows R). It will be appreciated that reversing the
polarity of the biassing magnet 182 can reverse the offsetting
magnetic bias.
FIG. 16 is a cross-sectional view of an inductive device 190
according to another alternative embodiment of the present
invention. The inductive device 190 is similar to the
above-described inductive devices in that it includes a magnetic
core 192 formed of a portion of a plurality of wires 194, a primary
winding 196, a secondary winding 198, an electromagnetic shield 200
and a biassing magnet 202. The plurality of wires 194 each have
first and second ends and partially encircle the windings 196 and
198, with the first and second ends of each wire facing each other
across a gap 204. The plurality of wires 194 complete a magnetic
circuit and form the shield 200.
In this embodiment, the gap 204 has a predetermined width and the
biassing magnet 202 is configured to be substantially disposed in
the gap 204. The biassing magnet 202 in this embodiment may, but
need not extend completely around the shield 200. It should further
be appreciated that the biassing magnet 202 can be replaced with a
plurality of biassing magnets.
The biassing magnet 202 is a permanent magnet and is arranged
adjacent the plurality of wires 194, so that it provides a magnetic
bias (indicated by arrows T) to offset a magnetic bias that is
introduced when a direct current component flows through either or
both of the windings 196 and 198 (indicated by arrows Y). It will
be appreciated that reversing the polarity of the biassing magnet
202 can reverse the offsetting magnetic bias.
The use of a plurality of wires to form a magnetic core yields an
efficient method for making an inductive device as set forth in the
earlier mentioned patents. In accordance with a preferred
embodiment of a method of this invention, FIG. 17 shows a step of
providing a magnetic core 220, which includes gathering a plurality
of wires 222 from a creel (not shown) to form a bundle 224, and
severing the bundle at a predetermined length with a knife 226 or
the like. The resulting magnetic core 220 is initially held
together by bands 228 or the like. The plurality of wires 222
pulled from the creel may all be the same diameter or may be a
combination of different diameters. Additionally, the plurality of
wires 222 may all have the same cross-sectional shape or may be a
combination of different cross-sectional shapes. The use of
different diameter wires and/or cross-sectional shapes allows for a
more dense packing of the magnetic core 220, thereby improving its
magnetic characteristics.
In accordance with the preferred method, two electric windings 230
and 232 are placed around the magnetic core 220. In a preferred
embodiment, the electric windings 230 and 232 are formed by winding
a coil of wire on a spindle (not shown), for slipping over the
magnetic core 220. Alternatively, the electric windings 230 and 232
may be wound directly on the magnetic core 220, as indicated by
arrow U in FIG. 18.
Advantageously, winding the electric windings 230 and 232 directly
on the magnetic core 220 provides a more efficient, and thus more
economical method of manufacturing by eliminating steps in the
prior art manufacturing methods.
Another advantage of winding the electric windings 230 and 232
directly on the magnetic core 220 is that the windings 230 and 232
assist in binding the wires of the magnetic core 220 tightly
together, thereby offering several mechanical and electrical
advantages. These advantages include tighter magneto-electric
coupling and greater control of vibrational noise from the
core.
FIG. 19 illustrates an alternative method for forming a bundle of
wires 224, a portion of which may be used as the magnetic core 220
in accordance with the present invention. Feeding one wire or a
plurality of wires 222 to a winder 234 forms the bundle 224.
However, one may also use a variety of wires having different
cross-sections (e.g., different diameters, cross-sectional shapes,
or cross-sectional areas) the wires being geometrically sized and
arranged to be densely packed. The plurality of wires are removed
from the winder 234, severed at a predetermined length to form the
bundle 224, and straightened as shown in FIG. 20. By appropriately
deforming the wound wires before severing, the ends will be
substantially square. As in the preferred method shown in FIG. 17,
bands 228 or the like hold the bundle of wires 224 together thus
forming the magnetic core 220.
With the electric windings 230 and 232 in place around the magnetic
core 220, the next step in the preferred method includes placing at
least one biassing magnet adjacent the plurality of wires. In this
embodiment, two biassing magnets 238 and 240 are placed at opposite
ends of the core 220. The biassing magnets 238 and 240 are
permanent magnetic rings. Preferably, the plurality of wires are
threaded through center holes of the biassing magnets 238 and 240
as shown in FIG. 21.
A preferred method includes configuring the plurality of wires 222
to substantially encircle the windings 230 and 232 and the biassing
magnets 238 and 240. FIG. 21 illustrates one exemplary manner of
encircling the plurality of wires 222 around the windings 230 and
322 and the magnets 238 and 240. The opposite ends of wires 222 are
initially spread by using a pair of cones 236 to force the wires
generally radially. The cores are moved toward one another as shown
by arrows W. Any conventional means may then be used to finish
configuring the wires 222 around the electric windings 230 and 232,
as generally shown in FIG. 1.
Those skilled in the art will recognize that the magnetic core of
an inductive device preferably forms a complete magnetic circuit.
In a preferred embodiment, with the plurality of wires
substantially encircling the electric windings and the magnetic
element(s), the ends of the wires substantially meet. In other
embodiments, the ends may overlap. In accordance with a preferred
embodiment, the wires are preferably prepared by having their ends
cleaned; then, when the ends of the wires meet, they are held
together by band or other means of connection. Alternatively, the
band may be used in conjunction with or be replaced by a fine iron
or steel wire wrapped transversely around the device or around the
wires adjacent a top or bottom of the device.
The plurality of wires form an electromagnetic shield. The device
made in accordance with a method of the present invention may
therefore be used in electrically noisy environments without
adversely affecting or being adversely affected by surrounding
components.
It will be understood that the present invention provides a highly
efficient method for making an inductive device and a highly
efficient inductive device. In addition, the utilization of a
magnetic element with a wire core inductive device adds a bias to
the generated magnetic flux, thus allowing for higher levels of
alternating current before saturation occurs when operating in an
environment, which includes a direct current component.
While the aforementioned embodiments include biassing magnets that
are permanent magnets, it should be appreciated that any of the
biassing magnets of this invention may be a permanent magnet or an
electromagnet, as well as a plurality of and/or combination of the
foregoing.
It should also be appreciated that any of the biassing magnets in
the aforementioned embodiments may be affixed or attached to the
inductive devices in a variety of manners, including but not
limited to: a band, a wire, an adhesive, or other matrix material,
or any other suitable means. The matrix may include magnetic
particles such as a magnetically active powder. When a matrix
material having magnetic particles is used, it may be desirable to
energize the winding(s) with a dc current to orient the particles
prior to hardening of the matrix material.
Further, it should be appreciated that although the foregoing
embodiments illustrate inductive devices that are transformers, it
should be appreciated that the invention is not limited to
transformers.
It should be appreciated that the shape of the inductive device
according to this invention is not limited to the generally
cylindrical shape of the illustrative embodiments. An inductive
device according to this invention may be of any shape suitable for
a specific application.
The foregoing descriptions of preferred embodiments of the
invention have been presented for purposes of illustration and
description. The descriptions are not intended to be exhaustive or
to limit the invention to the precise forms disclosed. Obvious
modifications, variations or combination of embodiments are
possible in light of the above teachings. The preferred embodiments
were chosen and described to provide an illustration of the
principles of the invention and its practical application to
thereby enable one of ordinary skill in the art to utilize the
invention in various embodiments and with various modifications as
are needed for the particular use contemplated. Various changes may
be made without departing from the spirit and scope of this
invention.
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